When you need a diff tool online, here they are. =)
http://www.diffchecker.com/diff
– copy-n-paste text
– have a URL to refer back to the diff result
http://www.diffnow.com/
– support text, file upload, and URL input
– can compare microsoft office documents (doc, xls, ppt)
http://www.quickdiff.com/
– copy-n-paste text
BrianChan.us 
you can find it handy too http://www.diff-online.com (for text comparision)
Contains this :
– copy-n-paste text
– have a URL to refer back to the diff result
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